Method of and apparatus for molding fibrous pulp articles



June s. 1 MQNTAGUE' Erm. 2,320,789 METHOD- br' AND Arrannus FOR MOLDINGFIBRoUs,.i=uLP ARTICLES Filed Oct. 18, 1959 i; s 1 IV mvmoiz. Stephen F.Montague ATTORNEY.

Patented June 3, 1943 v I METHOD OF AND APPARATUS FOR MOLDING FIBR/OUSPULP ARTICLES Stephen F. Montague, Oswego, and Lee D. Pierce,

Fulton, N. Y. assignors to Berst-Forster-Dixfield Company, -New York, N.Y., a corporation of Maine Application October 18, 1939, Serial No.299,936

4 Claims.

This invention relates to improvements in the method of making moldedpaper pulp articles and is directed alsoto a pressure head useful in vthe carrying out of the method.

It has heretofore been common practice in the making of molded pulparticles to compress the pulp between perforated dies and, as pressureis applied, the pulp is formed into the desired shape, while theresidual water is squeezed out through the perforations of one or bothdies. It is found in practice, however, that the nature of the pulpacted upon is such that it tends to clog the openings in the dies, withthe result that water is trapped in the pulp and consequently thearticle, as it leaves the dies contains so much water that prolongedapplication of heat to the formed articles is necessary to adequatelydry them.

One object of the present invention is to per-- fore practised. Weemploy complementary perforated dies as heretofore, but instead ofdepending solely upon the pressure of the dies to squeeze the water fromthe pulp, weforce compressed air through the perforations of one die,thence through the pulp and out through the perforations in the otherdie. In this way we utilize the pressure of the dies to squeeze out thewater and at the same time force out additional water by the passage ofcompressed air through the diesand through the pulp while the latter isunder pressure. In other words, we accompany the mechanical pressure ofthe dies with the flowof compressed air through the pulp, to entrain andcarry off residual water and at the same time preclude clogging of theperforations.

Another difflculty which has long vexed the industry is the tendency ofthe pulp to squeeze from between cooperating dies and form at theperiphery of the article thus'molded, protruding fibers, which, whendried produce a rough and undesirable edge which in some cases must betrimmed or cut oil. g

A further object of the present invention, therefore, is to obviate theformation of protruding fibers at the periphery of the articles so thata smooth edged article may result.

-We have been able to efiiciently accomplish this latter object bydirecting a blast of compressed air against the outer peripheral edge ofthe molded article, while the latter is under compression between thedies, for we have found that such a blast of compressed air will cause amatting of the fibers at the edge of the article and produce a smoothfinished edge.

The die which we preferably employ for the carrying out of the foregoingmethod comprises, in one preferred practical form, a hollow perforatedpressure head interiorly chambered, with the perforations disposedthroughout the molding face in spaced apart relation and leading from achamber in the pressure head to the molding face of said head. Themolding face is covered by a screen mesh shaped to conform therewith andcover the perforations so that pulp cannot enter thereinto. The pressurehead is preferably provided with an additional chamber communicatingwith a plurality of nozzles, positioned peripherally of the pressureheadand inclined so as to direct compressed air, fed from said chamber,intothe joint between the pressure head and a cooperating die, for thepurpose of matting the fibers of .the interposed pulp and producing asmooth edged article. Suitable means is provided for feeding air underappropriate pressure or pressures to the respective chambers of thepressure head and for controlling this flow of air as may be desired toaccomplish the results specified.

Experience has shown that, when the pressure dry them. Moreover theedges of these articles are smooth and lack that furry appearancecommonly found in articles as heretofore made.

Features of the invention, other than those adverted to, will beapparent from the hereinafter detailed description and claims, when readin conjunction with the accompanying drawing.

The accompanying drawing illustrates one practical embodiment ofapparatus for carrying out the method of this invention, but the con- Inthe preferred form of this invention, the.

pressure head comprises a molding plate 9, a

back plate 2 and a cover plate 3. The exposed face Ia of the moldingplate constitutes the I molding face thereof. It has a contourappropriate to the article to be molded and is adaptedto be covered byan overlying relatively fine mesh screen I, which conforms to itssurface and is held in place by a supporting ring 6 peripherallyembracing the molding plate. This ring 6 may have a forced fit or it maybe attached by screws,

or it may have threaded engagement with the die plate. While screens ofvarious mesh may be used in this connection, a 40 mesh screen, has beenfound to give satisfactory results,

The back portion of the moldingv plate is hollowed out to form, withinits body, a chamber 1 into which air may be fed through a hole 8 in thecover plate and a tapped hole 9 in the back plate. The molding plate andback plate are bound tightly together by the screws 4 which thread intobosses ID in the molding plate, as shown, andin order to insure againstpressure leakage between these plates, the molding plate is providedwith a marginal flange ll fitted into a registering channel l2 in theback plate.

Compressed air, fed into the chamber 1, from. 2

which extend through the plate to the molding tions I3 is adapted, byvirtue of its inherent pressure, to force its way through the pulparticle compressed between the molding face and the complementary faceof a cooperating die, indicated 'in dotted lines at It, which isperforated for the escape of such air. The passageof this air, asstated, causes the residual water of the pulp to be evacuated from thearticle between the dies, so that at the conclusion of the pressingoperation, the pulp will be relatively firm and free from water content.The presence of the screen over the perforations l3 serves to precludethe clogging of these. perforations by the pulp and assures the passage"of compressed air therethrough without interference.

Another advantage of the screen mesh is that it forms in the contiguousface of the molded article a symmetrical pattern which is more sightlythan a flat fiber "matted surface. If the die of the present inventionis used, as specified,

as a compression die cooperating with a forming die, this symmetricalpattern will be present in the article when it is delivered from thecompression-die and if it is thereafter acted upon by one or moreadditional dies having mesh screen faces, these latter faces will, inturn, apply their .own particular mesh screen pattern and the resultingaggregate will constitute a relatively I smooth surface of pleasingappearance.

It will be noted from Figure 2 of the drawing that the-cover plate issecured to the backplate y screws is and that the back face of the back11a" through a, tapped boss 11. IErom this air sage I! to an annularchannel is, formed in the periphery of the molding face within andadapted to be closed by the screen attaching ring 6. This screenattaching ring is provided, at closely spaced. apart intervalscircumferentially thereof, with holes '20 bored in inclined relation tothe face of the ring and constituting nozzles, so that air dischargedtherethrough .will be directed against the outer edge of the artic1e,,asthe latter is molded between the pressure head and the cooperating dieH. The inclined holes may conveniently be about in diameter and spacedabout V apart, so as to form around the outer periphery of the pressurehead a substantially frusto-conical curtain of compressed air directedagainst the outer edge of the pulp article operated upon. In the showingof Figure 2, this blast of air will be directed within the peripheralflange of the cooperating die It and will serve to blow down and mattthe fibers at the outer edge of the article in such manner as to producea smooth uniform edge in the finished molding.

The pressure of air supplied through the n'ozzles 20 will largely dependupon the character of the pressure of the air supplied through theperforations it of the molding face, for the w purpose of extractingwater from the article, but for ordinary operation, we have found thatsubstantially the same pressure may be supplied for both purposes. Insome cases we may artificially heat the air, used for either or bothpurposes, but this is optional. In practice the air streams used forthese different purposes are controlled by appropriate air valves,preferably cam actuated, so as to be synchronized with the operations ofthe machine in which the pressure headis used.

The mounting of the pressure head of this invention in cooperativerelation with the other parts of the machine with which it is to beused. may be accomplished in any desired way, but for illustration wehave shown the back plate I as provided therein with a number of tappedholes 2| adapted to receive attaching studs for this P po It will havebeen noted from the description of the structure shown in the drawing,that the pressure head of this invention is operated in accordance witha method quite different from those heretofore employed in the moldingof paper pulp articles. As previously stated, it has generally been thecommon practice tocompress pulp between dies which were perforated,sO-thflt the water of the pulp could be squeezed out through holes inone or both dies. If these holes become clogged with the pulp duringthis operation, the water was more or less trapped and satisfactoryevacuation thereof was out of the question.- In accordance with thepresent invention, in contradistinction, the pulp is compressed between\the dies while air under sufllciently high pressure is forced throughperforations in one of, the dies and through the pulp, to effectuallypropel water out through the perforations in the other die. In otherwords, the pre ent invention'includes the method steps of ompressingpulp and simultaneously forcing air through the pulp, as itiscompressed, for'the purpose of evacuating the water therefrom.

ing the molding thereof, butwe believe we are the first to actuallyforce water out of pulp by chamber l6, compressed air is fed through apasis forcing air through the pulp body hi u; 1

of the pulp operated upon and the same is true We are 'of course awarethat air under suctionor pressure has been used to carryoif watersqueezed from pulp durwater from the pulp as described, exclusively ofthe method of producing the. smooth edged articles,-and, conversely, wemay use the method of producing smooth edged articles withoutnecessarily employing the method of extracting the water. For bestresults, however, both of these methods are concurrently employed;Likewise,

.and with respect more particularly to structure,

the pressure head may be made to carry out either method to theexclusion of the other, al-- though the best results are obtained whenthe structure is such as to concurrently carry out both. Y

In the accompanying drawing, we have shown the pressure head as built upof a number of plates to-provide the air chambers to which we havereferred. This constitutes a convenient method of fabricating thepressure head, but we wish it understood that the structure may beotherwise formed withoutdeparting from this invention.

The foregoing detailed"description sets the invention in its preferredpractical form, but

the invention isto be understood as fully commensurate with the appendedclaims. Having thus fully described the invention, what we claim as newanddesire to secure by Letters Patent is: v

1. A die for molding fibrous pulp, having a molding face against whichan article of fibrous pulp is adapted to be molded, said die havinggaseous pressure'outlets arranged about the entire periphery fo the dieand peripherally of and spaced from the margin of said molding face andforth' positioned to direct a blast of compressed gas to impingedirectly against the entire peripheral edge of the article in engagementwith said face to blow down and mat the pulp fibres at said edge.

2. In the method of molding fibrous pulp articles, the steps whichcomprise compressing fibrous pulp between dlesinto an article of thedesired shape, and directing a blast of compressed gas to impingedirectly against the entireperipheral edge of said article while thearticle is held under compression between the dies, the pressure of saidgas being sufliciently forceful to blow down and'mat the pulp fibres atsaid edge.v

3. In the method of molding fibrous pulp articles, the steps whichcomprise compressing fibrous pulp between molding dies to formthe pulpinto the desired shape, and simultaneously directing a blast ofcompressed gas into the joint between the dies and directly against theedge of the pulp article, the pressure of said gas being sufficientlyforceful to blow down and mat the pulp fibres which tend to squeeze frombetween the dies, for the production of a smooth edge.

4. A die for molding fibrous articles having therein a plurality ofchambers and provided exteriorly with a molding face against which anarticle of fibrous pulp is adapted to be molded and through which facepassages lead to one of the chambers in the die, another chamber of thedie having outlets arranged about the entire periphery ot the die andperipherally of and spaced from the margin of the molding face and'po-'sitioned to direct a blast of compressed gas to impinge directlyagainst the entire peripheral edge of the article in engagement withsaid face to blow down and mat the pulp fibres at said edge, and meansfor supplying compressed gas to the latter chamber of the die.

STEPHEN F. MON'IAGUE. LEE n. PIERCE.

